(Transcript of audio with descriptions. Transcript includes narrator headings and description headings of the visual content)

(Speaker)
As the brain develops, the majority of axons become myelinated. In this process, nearby glial cells literally "reach out" and wrap axons with adjacent segments of a fatty substance that functions as a sort of insulator for the axon membrane. Myelin disrupts the movement of the action potential along the cell membrane. This disruption forces the electrical signal to "jump" through the axon beneath the surface areas that are insulated by myelin. The electrical charge jumps to the next region on the axon that is not insulated by myelin. These regions are known as "nodes of Ranvier." At each node, the electrical impulse can be recharged by a strong flow of electrically charged particles entering through the membrane. The strengthening electrical impulse then jumps to the next node, where the process is repeated. Transmission of an electrical impulse is much more rapid (up to 10 times faster) in myelinated axons than in unmyelinated axons.